This document discusses water repellency in fabrics. It defines water repellent fabrics as those where water drops roll off rather than soaking in. A fabric's water resistance depends on fiber surface, porosity, and water impact force. It distinguishes water-repellent fabrics, which are permeable but resist water under low pressure, from waterproof fabrics, which have fewer pores and resist water under high pressure. The document outlines different types of water repellent finishes and several test methods used to evaluate water repellency in fabrics.
3. Definition
• water repellent fabrics are those which resist being
wetted by water, water drops will roll off the fabric.
A fabric’s resistance to water will depend on
• the nature of the fiber surface,
• the porosity of the fabric
• the dynamic force behind the impacting water spray.
4. Distinguish between water-repellent
and water-proof fabrics
water-repellent fabrics water-proof fabrics
i. Water Repellent Fabrics have
open pores and are permeable to
air and water vapour.
i. Water-Proof Fabrics have fewer
open pores and are less permeable
to the passage of air and water
vapour.
ii. Water-repellent fabrics will
permit the passage of liquid water
once hydro-static pressure is high.
ii. Water-Proof Fabrics are resistant
to the penetration of water under
much higher hydrostatic pressure.
iii. A fabric is made water-repellent
by depositing a hydrophobic
material on the fibre’s surface.
iii. however. Waterproofing requires
filling the pores as well as
depositing a hydrophobic material
on the fibre’s surface.
10. Water repellent finishes
• Water repellents are chemical finishes
• Resist the penetration of water into the fabric
• Permits the passage of moisture or air through the fabric
• There are three types of water repellent finishes:
non-durable finishes
semi-durable finishes
durable finishes
11. Non-durable finishes
• This type of water repellent finish is usually based on
paraffin wax-aluminum acetate emulsion.
• non-durable finishes are easily removed in laundering or
dry-cleaning.
• non-durable finishes do not provide satisfactory
resistance to liquids.
• Examples:
Aquarol AX,
Aridex WP,
Dryon,
Repelex etc
12. Semi-durable finishes
• These are wax or salt solutions.
• They are emulsified off the fabric in laundering.
• They ate resistant to dry-cleaning.
• Examples:
Bishopel,
Dryon A-B,
Nalan W etc
13. Durable finishes
• There are several types of durable water repellents, such
as
1. Pyridinium compounds
It is Applied to cotton,
linen & viscose rayon
fabrics.
It also endures repeated
washings as well as
dry-cleaning.
It improves the fabric’s
appearance.
2. Melamine resins &
stearamides compounds
It is used on cotton,
rayon etc.
These have excellent
repellency and good
tolerance to laundering.
3. Silicone compounds
These are excellent
water repellents.
The finish is usually
more resistance to dry
cleaning than to
laundering.
Examples: Aerotex, Hydro-Pruf, Zelan, Zepel etc.
15. Several test methods of water repellency of
fabrics
AATCC TM22: Water Repellency-Spray Test
AATCC TM35: Water Resistance: Rain Test
AATCC TM42: Water Resistance: Impact Penetration Test
AATCC TM70: Water Repellency-Tumble Jar Dynamic
Absorption Test
AATCC TM127: Water Resistance: Hydrostatic Pressure
Test
16. Working procedure of spray test method
• Step-1: The sample fabric is mounted on a metal hoop.
17. Working procedure of spray test method
• Step-2: Then the metal hoop attached with sample fabric
is fixed on the instrument at 45ᵒ angle.
18. Working procedure of spray test method
• Step-3: Now the beaker is filled with 250 cc water.
19. Working procedure of spray test method
• Step-4: pour the distilled water into the funnel.
20. Working procedure of spray test method
• Step-5: spray the whole quantity of water on the test
specimen for a period of 25 - 30 sec.
21. Working procedure of spray test method
• Step-6: After spraying has finished the sample holder is
removed and the surplus water removed by tapping the
frame 6 times against a solid object.